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Inaccuracies in estimated glomerular filtration rate in one Australian renal centre
Author(s) -
BROWN MARK A,
PIRABHAHAR SAIYINI,
KELLY JOHN J,
MANGOS GEORGE J,
MACKENZIE CALLIE,
MCCONACHIE PETER,
JANSSEN JULIA,
SMART RICHARD C
Publication year - 2011
Publication title -
nephrology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 61
eISSN - 1440-1797
pISSN - 1320-5358
DOI - 10.1111/j.1440-1797.2011.01453.x
Subject(s) - renal function , medicine , kidney disease , urology , creatinine , body surface area , gold standard (test) , cohort , population , epidemiology , environmental health
Background: Early identification of true renal disease (glomerular filtration rate (GFR) < 60 mL/min) results in better patient outcomes. There is now routine reporting in Australia of estimated GFR (eGFR) in all patients over age 18 who have serum creatinine measured, calculated by the Modification of Diet in Renal Disease (MDRD) formula, which was validated in an American Caucasian cohort. Significant clinical decisions and prognosis are often made on the basis of this calculation. Aim: To assess the accuracy of three estimates of GFR in an Australian population by comparing eGFR obtained by the abbreviated MDRD (aMDRD), Cockcroft–Gault corrected for body surface area (BSA) (CG) and Chronic Kidney Disease Epidemiology (CKD‐Epi) formulae with a gold standard, isotopic 51 Cr‐ethylenediaminetetra‐acetic acid ( 51 Cr‐EDTA) GFR. Methods: Patients referred with an eGFR of <60 mL/min reported by the aMDRD formula underwent isotopic measurement of GFR (over 4 h) and had eGFR calculated using CG corrected for BSA, aMDRD and CKD‐Epi formulae. Data were analysed using Bland–Altman plots and regression analysis to compare methods; bias, precision and the proportion of patients correctly stratified by stage of chronic kidney disease (CKD) were also compared according to the three estimates of GFR, using 51 Cr‐EDTA GFR as the gold standard. Results: A total of 139 patients were recruited (female 45%), mean age 64 years and mean serum creatinine 212 µmol/L. The mean GFR (SD) (mL/min per m 2 ) for isotopic, CG, aMDRD and CKD‐Epi were 47 (28), 37 (20), 32 (17) and 33 (18) ( P = 0.001). CG (57%) was more likely to correctly stage CKD than aMDRD (37%) or CKD‐Epi (37%), and absolute bias was significantly lower using CG than either other method ( P = 0.001). Conclusion: In this small Australian population the CG formula corrected for BSA agreed more closely with isotopic GFR and correctly staged patients with CKD more often than the aMDRD or CKD‐Epi formulae. It is important that each renal Unit considers the accuracy of estimates of GFR according to their population demographics.